Tire pressure monitoring systems (TPMS) on vehicles are generally required in the U.S., with Europe and countries in Asia to follow. The legislation mandating the use of TPMS typically sets a pressure warning threshold level which is monitored by wheel-based units, or wheel modules, in direct TPMS. The wheel modules are mounted inside of each tire, such as on the rim, valve, or in-tire, in order to periodically or continuously monitor the inflation pressure of the tire.
Each wheel module typically includes a pressure sensor, control logic such as a microcontroller, a power source such as a battery, and a radio frequency (RF) transmitter that communicates information from the wheel module to a central TPMS receiver mounted elsewhere in the vehicle. Some wheel modules also comprise an acceleration sensor for determining when the vehicle is in motion in order to conserve battery life.
There are significant power constraints on the wheel modules. For example, a typical wheel module should be able to operate with the same battery for at least five years. Such demands make prolonged wheel module operation or operation when data cannot or should not be detected undesirable and increase the need for efficient communications between wheel modules and a central receiver.
Therefore, there is a need for improved operation and communication techniques in TPMS system wheel modules.